We met on the streets of Whitehall, central London, during the now infamous riots against capitalism earlier this year. Short and stocky, he sat on a bicycle, chatting nonchalantly to two anarchists as the police lines bore down upon us. With characteristic composure, he featured a quick glance behind him, then cycled off at a leisurely pace.

The next time I saw him he was being ejected from the Annual General Meeting of a multinational construction company, waving a video camera triumphantly above his head. His supporters cheered as the tuxedo-wearing funnyman remonstrated with angry and bemused shareholders in the street outside, about their support for the company?s work on a controversial project abroad.

And Mark Thomas, 37, comedian and de facto investigative journalist, is nothing if not controversial himself. His relentless diatribes against the excesses of big business, as well as the nuclear industry, arms trade and other ?cause celebres?, are well known to the millions of Britons who watch his late night TV show broadcast on Channel 4.

Thomas? acerbic style, and his ability to rile corporations, the military and government institutions, have made his shows a huge success. Some of his more notable programmes include the time he managed to pass himself off as a public relations consultant at an arms fair, and convince foreign generals to admit torture and human rights abuses as part of the ?training? he provided.

He also chased the head of the Export Credit Guarantee Department (ECGD) - which has provided British taxpayers? money to underwrite controversial projects overseas, such as the sale of Hawk jets to Indonesia, or the funding of the Ilisu Dam construction in Turkey/Kurdistan - all the way through a banking industry banquet, before trying to hand him the shirt taken from a Nigerian official. As a message about debt repayment, it proved far more effective than a letter writing campaign.

Not only that, but he has sailed over a US spy base in a hot air balloon; set up an observation platform to look into the Aldermarston nuclear weapons facility; and found that owners of stately homes were claiming tax relief for objects d?art, by claiming the pieces were available for public viewing, without ever allowing access to them. Thomas, of course, promptly turned up at these homes demanding access.

He makes use of a natural ?gift of the gab? and honest, amiable features, to gain access where few others could. Plus there is a team of eight researchers backing up his work, checking obscure rules and regulations that few would otherwise know even existed. Some have even said that Thomas - a standup comedian by trade - is doing a job that was traditionally catered for by investigative journalists, and that with the dying of that breed, he is taking over. An occasional disgruntled journalist has even complained that he is infringing on their territory.

?We were looking at stories that weren?t coming out,? answers Thomas, leaning back on a chair in the offices of his London production company. ?We were breaking stories that people didn?t know about, really building up our primary research, and so we?ve almost accidentally ended up as journalists.?

Chain smoking an ubiquitous cigarette and peppering his language with frequent curses, Thomas talks enthusiastically, explaining that his material has become more and more political over the years. So how does a comedian end up doing investigative work, I ask?

?Ah!? he laughs tiredly, as though he has heard the question many times before. ?Accident really. I started as a comedian about 15 years ago, and when you start doing it first of all, you just want to make people laugh. And then you learn that you can make people think, have emotions and look at things again. For me, it was about continually trying to look again at something. Whether I would be talking about sex or politics or whatever, there?d always be something be interesting there that would make people look again.?

So he had a sense of personal conviction? ?Yeah, I guess so.? What about the motivation, though? Why tackle such subjects - is it some form of altruism?

?Anger, I think, is the motivator here,? he laughs back at me. ?Also, if this is about our money being used, we can cow down to government and let them get away with it, or say no, it isn?t going to happen. This is our money and it raises all sorts of important questions about accountability and democracy.?

He takes a quick puff on the smoldering stub of his cigarette. ?It?s our money, we should know what it?s being used for. It?s constantly used to support deals with dictatorships, countries with very poor human rights records. In the last accounts I?ve seen, arms trade made up 52 percent of the ECGD?s underwriting.?

Not surprisingly, Thomas is proud of his south London working class roots. With his mother a midwife and father a builder, Thomas won a scholarship to Christ?s Hospital public school in West Sussex. ?It kind of gave me a crash course in class awareness going to that school,? he muses. ?I think class is important. If we?re all middle class now that?s bloody great, but there?s some people who haven?t heard yet and cracked open the chianti!?

Studying Theatre Arts at college in Wakefield, West Yorkshire, he entered political life via the Miner?s Strike which dominated the pit villages in the surrounding countryside. ?This was a particularly politicising event for me,? says Thomas. ?Although I was always somewhere between a Trot(skiyte) and anarchist? he adds, smiling.

?One of my proudest possessions is a pit badge commemorating the strike.? he continues. ?There were only three left over from the strike, so they had a vote who to give them to, and I was one of the people chosen, just as a mark of thanks. It was an incredibly emotional moment - as was the march back to work, and that memory will never leave me,? he explains, talking softly, ?as the colliery band and supporters and miners walked back. As we went past the school, there was this incredible moment when all the teachers let out the kids to see their dads go back to work. The kids were singing Solidarity Forever, watching their dads going back to work, and it was incredibly emotional, incredibly...?

When he left college he went straight into standup. ?I always wanted to make standup interesting, political to some extent, and it was just like over the years that the standup became more and more political.? He formed a slot called Cutting Edge at the legendary Comedy Store in London. ?We?d write a show each week about topical issues and we?d try and get behind the news a bit. During the Gulf War we?d be doing gigs and getting heckled by squaddies, for example. It was one of the few places you could hear any discontent.?

After that, he says his material became noticeably more political. He was resident comic on a TV show called Saturday Zoo, which featured then unknowns like Steve Coogan, and John Shuttleworth. Thomas would appear every other week as a live standup and remembers ?we?d get into huge rows, I?d end up threatening High Court judges on live TV!?

He still believes he retains ?a sense of fun? to his shows and says that although he has no idea about his future plans, ?we?ve still got enough topics, we?ve still got enough shit for us to talk about for a long time yet!?